Effect of ZnSO4, MnSO4 and FeSO4 on the Partial Hydrogenation of Benzene over Nano Ru-Based Catalysts

Abstract

Nano Ru-based catalysts, including monometallic Ru and Ru-Zn nanoparticles, were synthesized via a precipitation method. The prepared catalysts were evaluated on partial hydrogenation of benzene towards cyclohexene generation, during which the effect of reaction modifiers, i.e., ZnSO4, MnSO4, and FeSO4, was investigated. The fresh and the spent catalysts were thoroughly characterized by XRD, TEM, SEM, XPS, XRF, and DFT studies. It was found that Zn2+ or Fe2+ could be adsorbed on the surface of a monometallic Ru catalyst, where a stabilized complex could be formed between the cations and the cyclohexene. This led to an enhancement of catalytic selectivity towards cyclohexene. Furthermore, electron transfer was observed from Zn2+ or Fe2+ to Ru, hindering the catalytic activity towards benzene hydrogenation. In comparison, very few Mn2+ cations were adsorbed on the Ru surface, for which no cyclohexene could be detected. On the other hand, for Ru-Zn catalyst, Zn existed as rodlike ZnO. The added ZnSO4 and FeSO4 could react with ZnO to generate (Zn(OH)2)5(ZnSO4)(H2O) and basic Fe sulfate, respectively. This further benefited the adsorption of Zn2+ or Fe2+, leading to the decrease of catalytic activity towards benzene conversion and the increase of selectivity towards cyclohexene synthesis. When 0.57 mol·L−1 of ZnSO4 was applied, the highest cyclohexene yield of 62.6% was achieved. When MnSO4 was used as a reaction modifier, H2SO4 could be generated in the slurry via its hydrolysis, which reacted with ZnO to form ZnSO4. The selectivity towards cyclohexene formation was then improved by the adsorbed Zn2+.

Ru-Loaded Biphasic TiO2 Nanosheet-Tubes Enriched with Ti3+ Defects and Directionally Deficient Electrons as Highly Efficient Catalysts in Benzene Selective Hydrogenation

“…Initially, 0.5 g Ru/TNSTs catalyst, 60 mL H 2 O, and 12 g ZnSO 4 •7H 2 O were introduced into the kettle. Among many possible additives [9,54,55], ZnSO 4 •7H 2 O is widely recognized as the best additive to enhance the selectivity of cyclohexene effectively [5,49]. Subsequently, 30 mL of benzene was added to the storage tank.…”

“…Such catalysts should be capable of modulating the relative rates of the two-step hydrogenation reactions, i.e., benzene to cyclohexene and cyclohexene to cyclohexane [6][7][8], thereby yielding more cyclohexene product. Currently, non-loaded RuZn catalysts are widely used in industry [9,10], but they have drawbacks, including containing a high amount of precious metal Ru, typically greater than 80% by weight, and poor catalyst stability. Additionally, the zirconia additive, used to prevent the agglomeration of RuZn, is challenging to control the dispersion.…”

Multifunctional Nanomaterials: Synthesis, Properties, and Applications 2.0

“…In the seventh article (research) [7], Yuan-Chang Liang et al reported the development of a brush-like Fe 2 O 3 -ZnO nanostructures towards NO 2 gas sensing based on the control of appropriate material synergistic effects. Further, Zhikun Peng et al [8] reported the influence of ZnSO 4 , MnSO 4 and FeSO 4 on the partial hydrogenation of benzene over nano Ru-Based catalysts. The ninth published research article by Xiaoyu Yu et al [9], discussed the development of an optimized synthesis approach for ZnO quantum dots (QDs) modified with polyvinylpyrrolidone (PVP40) which can potentially be applied in the fields of photoluminescence and photodynamic tumor suppression.…”